The present invention relates generally to snow plows for use with light and medium duty trucks, and more particularly to an improved snow plow with blade trip springs which are mounted using brackets located to direct the forces of the springs in directions which are orthogonal to the axis upon which the plow blade pivots, thereby increasing the predictability of the tripping forces exerted by the trip springs as well as eliminating lateral trip spring forces which could warp the plow blade.
Once the exclusive domain of municipality-operated heavy trucks, snow plows have been used with light and medium duty trucks for decades. As would be expected in any area of technology which has been developed for that period of time, snow plows for light and medium duty trucks have undergone tremendous improvement in a wide variety of ways over time, evolving to increase both the usefulness of the snow plows as well as to enhance the ease of using them. The business of manufacturing snow plows for light and medium duty trucks has been highly competitive, with manufacturers of competing snow plows differentiating themselves based on the features and enhanced technology that they design into their products.
When plowing snow, a not infrequent occurrence is striking an object which is concealed beneath the snow. This occurs particularly often when plowing roads which are not paved, such as, for example, gravel roads or dirt roads. Since roads being plowed are typically frozen, it is common for an object of significant size to become frozen into the road. For example, medium size rocks or sticks which would not present a significant obstacle were they loose on the surface of the road can present a problem when they are frozen into the surface of the road and concealed beneath a layer of snow. In addition, when significant snow depth covers the area being plowed, the operator may miscalculate and drive the snow plow into a fixed obstacle such as a curb.
For this reason, snow plow blades have been manufactured for some time with a blade trip mechanism which allows the bottom of the blade to yield upon substantial impact. This is typically accomplished through the mounting of the snow plow blade on its support structure using a pivoting mechanism. The snow plow blade is mounted onto the support structure at a position between eight and sixteen inches above the ground in a manner which permits the bottom of the snow plow blade to pivot back when an object is struck. Simultaneously as the bottom of the snow plow blade pivots back, the top of the snow plow blade will pivot forward.
This movement between the normal plowing position of the snow plow blade to the position in which the bottom of the snow plow blade pivots fully backward is referred to as blade tripping. The movement of the snow plow blade from the normal plowing position to the tripped position is resisted by two or more strong trip springs which are mounted behind the snow plow blade, typically running from positions near the top of the snow plow blade to the snow plow blade support structure. Even when the snow plow blade is in its normal plowing position, the trip springs are under tension. Accordingly, it will be appreciated that when the bottom of the snow plow blade is forced backward, the trip springs will provide a strong resistance to the movement, tending to absorb some of the force of the impact of the snow plow blade with the object which has been struck.
In a typical embodiment, the snow plow blade is supported at two pivot points on the right and left sides of the snow plow blade by a swing frame. The snow plow blade has a plurality of vertically extending curved ribs which are connected between top and bottom plow frame members, and two of these ribs have apertures located between approximately eight and sixteen inches from the bottom of the snow plow blade. The snow plow blade is pivotally mounted to the swing frame using these apertures. The trip springs are mounted between the snow plow blade and the swing frame to provide the tripping resistance force.
The trip springs are mounted to the snow plow blade using apertures located either in the ribs or in the top frame member, or using brackets mounted onto one or more of these members. The trip springs may be mounted at one end to the top frame member and the ribs from which the snow plow blade is pivotally supported. The other ends of each of the trip springs are mounted to the snow plow blade support structure, typically using brackets which may be mounted, for example, on the swing frame. The points of connection of the trip springs on the swing frame or other snow plow blade support structure are typically located closer to the center of the snow plow than is the point of connection of the trip springs to the snow plow blade.
Although the predominant force exerted by the trip springs on the snow plow blade is orthogonal to the axis on which the snow plow blade pivots, a significant portion of the force is exerted in a lateral direction which is parallel to that axis. This component of the spring force is detrimental to the structural integrity of the snow plow blade frame, which is not constructed to resist forces in a lateral direction. Although the trip springs are located on both sides of the snow plow blade, and the lateral forces exerted by them thus tend to offset, over time their presence can cause blade distortion or other damage. In addition, it will be appreciated by those skilled in the art that since not all of the force exerted by the trip springs is in the direction orthogonal to the axis on which the snow plow blade pivots, the trip springs must be larger in order to provide the desired force in this orthogonal direction than they would otherwise be if all of the force which they exerted were in this orthogonal direction.
It is accordingly the primary objective of the present invention that it mount the trip springs on a snow plow in a manner whereby all of the force exerted by the trip springs is exerted in a direction which is orthogonal to the axis about which the snow plow blade pivots. It is a closely related objective of the present invention that it provide mounting brackets which facilitate the mounting of the trip springs in a manner which eliminates the exertion of any lateral force by the trip springs. It is a further related objective of the present invention that it minimize the size of the trip springs by ensuring that all of the force which they exert is directed properly to provide the required force in the requisite direction.
It is another primary objective of the present invention that the force exerted by the trip springs is exerted proximate a plane which is orthogonal to the pivot points at which the snow plow blade is mounted to the snow plow blade support structure. It is a related objective that the force of the trip springs is exerted on appropriate areas of the snow plow blade so that any potential distortion of the snow plow blade is inhibited. It is a further objective of the present invention that it facilitate the use of either a single trip spring on either side of the snow plow blade or two trip springs on each side of the snow plow blade.
The snow plow trip spring mount of the present invention must also be of a construction which is both durable and long lasting, and it should also require little or no maintenance to be provided by the user throughout its operating lifetime. In order to enhance the market appeal of the snow plow trip spring mount of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the snow plow trip spring mount of the present invention be achieved without incurring any substantial relative disadvantage.
The disadvantages and limitations of the background art discussed above are overcome by the present invention. With this invention, the trip springs which control the tripping action of the snow plow blade are each mounted such that they exert force only in a plane which is perpendicular to the axis of rotation of the snow plow blade""s tripping movement. The snow plow blade itself is supported at two pivot points on the right and left sides of the snow plow blade by a swing frame, and the trip springs are each mounted between the swing frame and the snow plow blade.
The snow plow blade has a plurality of vertically oriented curved ribs which are connected between top and bottom plow frame members, and two of these ribs have apertures located between approximately eight and sixteen inches from the bottom of the snow plow blade. The swing frame itself is based upon a rectangular steel swing frame tube, which has a pivot made of steel tubing extending between two opposite sides of the swing frame in a location intermediate the ends of the swing frame. The swing frame will be pivotally supported by a snow plow frame, which in turn will be mounted onto the front of a truck. The swing frame has a pair of parallel blade pivot mounts located at each end thereof, which blade pivot mounts extend forwardly from a swing frame tube upon which they are mounted.
Located near the front of each of the blade pivot mounts are apertures which are aligned in each pair of blade pivot mounts. Each pair of blade pivot mounts will receive a portion of one of the ribs on the snow plow frame which have the apertures therein, with one of the blade pivot mounts in each pair being located on either side of the rib to which that side of the swing frame is being mounted. A pin extends through the aligned apertures on each side of the snow plow blade to pivotally mount it on the swing frame.
Located on the swing frame near each of the ends thereof is a bracket for mounting one end of one or two trip springs, the other ends of which trip springs will be mounted to corresponding brackets which are mounted onto the frame of the snow plow blade. In the preferred embodiment, the brackets on the swing frame are mounted on the blade pivot mounts, and the brackets on the snow plow blade are mounted on the ribs of the snow plow blade which are pivotally mounted to the blade pivot mounts on the swing frame. Since these brackets are aligned with each other, the trip springs mounted between the corresponding pairs of brackets will be oriented front to rear, and as such will not exert any lateral pull on the snow plow blade.
In the preferred embodiment, two trip springs are mounted at each side of the snow plow blade. Alternately, a single trip spring may instead be used on each side of the snow plow blade. As the snow plow blade pivots between its trip return position and its tripped position, the trip springs always exert force only within a plane which is parallel to the axis of the pivoting movement of the snow plow blade.
It may therefore be seen that the present invention teaches an apparatus and method for mounting the trip springs on a snow plow in a manner whereby all of the force exerted by the trip springs is exerted in a direction which is orthogonal to the axis about which the snow plow blade pivots. The mounting brackets of the present invention facilitate the mounting of the trip springs in a manner which eliminates the exertion of any lateral force by the trip springs. The size of the trip springs required by the present invention is minimized by ensuring that all of the force which they exert is directed properly to provide the required force in the requisite direction.
The force exerted by the trip springs of the snow plow trip spring mount of the present invention is exerted proximate a plane which is orthogonal to the pivot points at which the snow plow blade is mounted to the snow plow blade support structure. In addition, the force of the trip springs is exerted on appropriate areas of the snow plow blade so that any potential distortion of the snow plow blade is inhibited. The snow plow trip spring mount of the present invention facilitates the use of either a single trip spring on either side of the snow plow blade or two trip springs on each side of the snow plow blade.
The snow plow trip spring mount of the present invention is of a construction which is both durable and long lasting, and which will require little or no maintenance to be provided by the user throughout its operating lifetime. The snow plow trip spring mount of the present invention is also of inexpensive construction to enhance its market appeal and to thereby afford it the broadest possible market. Finally, all of the aforesaid advantages and objectives of the snow plow trip spring mount of the present invention are achieved without incurring any substantial relative disadvantage.